Suspensions for lubricating and other purposes



Patented May 9, 1939 ,isam

'SUSPENSIONS FOR LUBRICATING AND OTHER PURPOSES Victor R. Abrams, EastOrange, N. 3., assignor to Sulflo Corporation of America, a corporationof Georgia 12 Claims.

This invention relates to freely flowing suspensions of finely dividedsolid particles of organic cants and grinding, lapping and polishingcompounds.

Stable, freely flowing suspensions areproduced,

in accordance with this'invention, by distributing through the desiredorganic liquid vehic les finely divided particles of 'solvatedhydrogenated castor oil wax having an elastic gel nature. This may beconveniently accomplished, 'for example, 15

vehicle at an elevated temperature and then cooling to form aiwaxyprecipitate, which, upon proper manipulation of the mixture, becomesbroken up into finely divided gel particles distributed throughout thevehicle, the gel particles being substantially in contact. The resultingmixture will be of free-flowing consistency if a suitably small amountof wax has been used.

The particles to be suspended, when distributed through this mixture ofvehicle and gel particles, are prevented from moving'by the gelparticles andthus are maintained indefinitely in a stable state ofsuspension. In other words, the wax is .-'used to effect a mechanicalsuspension of the particles without converting the mixture into asemi-solid or non-flowable state.

As indicated, the function of the solvated wax particles (gel particles)is not to increase the viscosity and thereby slow down the settling orris-' ing of the suspended particles, which would require that themixture be made of the consistency of a cake or paste tosecurereasonable stability as to suspended particles of greater thancolloidal size, but is to entrain the suspended particles andmechanically prevent movement thereof without .rendering the mixtureincapable of free flow.

wise be stably suspended in accordance with the invention. Colloidalparticles 'thus suspended 55 are rendered stably suspended not onlywhenin colloidal state but also in the event of agglomerat'ionintoparticles of greater than colloidal size, which is not true of particlesin ordinary colloidal suspensions.-

60 The gel particles in the suspension mixture are by dissolving a smallamount of the wax in the elastic in nature and resist deformation anddisplacement in a manner such that a small force will merely deflectthem without producing continuous motion, and a force in excess ofaminimum which depends upon the materials and conditions is required toproduce continued motion of any object present in a mass of theparticles. The result is that the gel particles, and other particlespresent, are prevented from moving through the mass, the force ofgravity or buoyancy on each particle being less than the minimum forcerequired for continuous motion. In this manner evensuch dense particlesas those of finely divided lead can be prevented from settling out, andfinely divided air bubbles can be prevented from rising and escaping.

In order to produce the above eifect, the gel particles must besum'ciently close together so that they cannot be merelycarried throughthe liquid vehicle without influencing each other, and this minimumrequirement may be readily determined by experiment in any desired case.

The wax-vehicle mixture capable of sustaining particles in stablesuspension may be broadly characterized as a mobile discontinuousgelatinous mass composed of particles of waxy elastic gel substantiallyin contact with each other and having the interspaces containing theliquid vehicle, "the particles to be suspended being distnbuted in orbetween the gel particlesandprevented from moving thereby."

The term gelcosityfis used to designate this property of mobile"discontinuous gelatinousmasses, and the degree of force required to produce continuous motion without such gel masses,

The higher the gelcosity, the greater the force needed to causecontinued motion of a particle vent sway. The vane i's'placed 'in themedium to be tested and the latter rotatedarertain amount, as by turningthe receptacle, whereupon the'vane will swing about its axis and thenreturn toward its initial rest position due to the restoring forceexerted y the wire. If the; medium' possesses the? property ofgelcosity, the vane will .not return completely, \but will come to restin a dig placed position. The greater the displacement the. greater thenice needed to cause continuous movement or now within the medium andhence the greater the gelcosity. If the mobile medium 'is' continuous,it can have no gelc'osity and the vane will slowly return to the initialposition even though the medium is highly viscous; while a medium ofhigh gelcosity will cause a large displacement even though of quite freeflowing consistency. In other'words, a displacement of the vane, whichmeasures a static equilibrium condition, is a consequence of thegelcosity and not of the above test, just as in the case ofnon-gelatinous liquids of high or low viscosity. An example of a mobilecontinuous gelatinous mass is a solution of raw rubber dissolved in apetroleum oil. This possesses the characteristics of elasticity,stringiness and may have a high viscosity, but an infinitely small forcewill produce flow and hence no gelcosity will be exhibited. A gelati--nous mass which has set", forming a solid jelly,

is also a continuous gelatinous mass, but of course is not mobile andexhibits the overall characteristics of a solid until broken up to forma discontinuous mass, and thus obviously does not possess thecharacteristics of a mobile discontinuous gelatinous mass containingdiscrete gel particles.

A representative hydrogenated castor oil wax (produced by hydrogenatingcastoroil to an extent resulting in a hard waxy product), is milkwhitein color, has a specific gravity of about 0.99 at 20 C., has a meltingor solidifying point in the range of about 171-178 R, an acid numberandan iodine number of about 3.

. The term "wax is applied to thehydrogenated castor oil in accordancewithtechnical usage, since this product is of waxy appearance and isgenerically similar to the so-called natural or true waxes in respect tomany properties.

Hydrogenated castor oil wax is relatively insoluble at room temperatureand thereabouts in most organic vehicles, and in many cases can besatisfactorily used in amounts of 1% or less (for example, with mineraloils, petroleum ether, petroleum naphtha, linseed oil, Cellosolve, andothers) It appears to approximate universality, as it has been found tobe satisfactory when of about 2, a saponification number of about 180,

used in amounts of 3% or less with the following liquids selected fromcommonly known oils and organic solvents: mineral oil, fish oil, 0 cornoil, soy bean 011, cotton seed oi, linseed oil (both raw and boiled),tung oil, polymerized tung oil, petroleumnaphtha (V. M. 8: P.),petroleum ether, benzene, toluene, xylene, coal tar naphtha, ethylalcohol (abs. and methyl acetate,

alcohol, isobutanol, acetone, amyl Cellosolve (ethylene glycol monoethylether), Methyl Cellosolve (ethylene glycolfmonomethyl ether), tricresylphosphate, turpentine, carbon tetrachloride and carbon disulfide.

Combinations of organic liquids can be used, that is, the liquid vehiclemay be comprised of one or more components. Pairs or groups of liquidswhich may be used individually with -a given wax may generally be usedin combination, if miscible with each other, as the vehicle. Forexample, the following combinations, among others, may be usedsatisfactorily with hydrogenated castor oil wax: linseed oil and mineraloil, linseed oil and naphtha, linseed oil and turpentine, and soy beanoil and Cellosolve. In

this way a thin liquid may be thickened," a thick tor oil,

liquid thinned, and other modifications and combinations made use of inpreparing the vehicle, as is well known in the art.

In the preparation of lubricants and of grinding and lapping compounds,non-volatile petroleum oil fractions are customarily employed asvehicles, and as little as 1-3% or less of the hydrogenated castor oilwax may be incorporated therewith to obtain stable suspensions of finelydivided solid lubricants and abrasives.

The organic liquid vehicles which may be employed in accordance with theinvention may be generically characterized as those in which the wax issolvatable or lyophilic, meaningthat the liquid is capable of beingdissolved in or adsorbed by solid wax particles to render themgelatinous, and in which the wax is relatively insoluble at normal roomtemperature (20 C. or 68 F.) and thereabouts.

If the wax is readily dissolved in the liquid at an elevated temperature(as disintguished from melting without dissolving), a mutualcompatibility exists indicating that at lower temperatures solid waxparticles will be solvatable (lyophilio) in the liquid. The wax-vehiclecombination should be such that it is freely flowing and possessed ofsubstantial gelocity (suspending power) throughout at least thetemperature range Ill-35 C. (50-95, F.) Hence the wax should have asolubility-temperature characteristic in the liquid such that no greatincrease of solubility occurs Within the limits of about 10-35 C.

(SO-95 F.), as otherwise if sufl'icient wax is employed to producegelcosity at the upper temperatures, there will be so much wax out ofsolution at the lower temperatures that the mixture will not be freelyflowing attemperatures to be expected under room conditions.

I prefer to employ liquid vehicles in which an amount of the wax notexceeding about 5% by weight, relative tothe vehicle, can be used toproduce suspending media which will be freely flowing and possessed ofsubstantial gelcosity throughout at least the temperature range of10-40" C. (50-104 F.), and this standard is met and exceeded by all ofthe various liquid vehicles heretofore named. For .example, a suspensionhaving a petroleum oil vehicle (such as a neutral oil of 28-32 Baumgravity) and containing about 1% of hydrogenated castor oil wax, will befreely flowing and stable at temperatures up to about 71 C. F.).

The relative insolubility of hydrogenated castor} oil wax in a number ofcommon organic liquid vehicles at room temperature and thereabouts, inwhich the wax is solvatable, is shown by the following table:

Solubility of hydrogenated castor oil wax grams Solvent P 1 1 c. c. ofsolvent- At 18-20 C. At 33 C.

Toluene Carbon tetrachloride...-; Carbon bisulflde.-.

Cellosolvex Ethyl alcohol (ab Methyl alcohol- Petroleum ether- MethylCellosolvc. Ethyl alcohol (95%) Lubricant suspensions may be preparedcontaining finely divided solid lubricant particles of greater thancolloidal size, such as flowers of sulfur and finely divided selenium,tellurium, talc, slaked lime, white lead, white zinc and cork dust.

As further exampla of suspensions to which the invention applies,mention is made of grinding, lapping and polishing mixtures containingsuspended particles of emery, carborundum, rouge, whiting, or similarsubstances.

The term solid particles", as used herein includes semi-solid or plasticparticles, such as particles of natural and synthetic resins.

The actual preparation of freely flowing susscribed in more detail. Allmethods involve the essential steps of distributing the wax in theliquid vehicle in the form of finely divided discrete particles andsolvating or gelatinizing the particles. These steps may be performedcon- .currently or successively; and if performed suecessively they maytake place in either order, that is, the wax may be finely divided andthen solvated of gelled, or may be gelled and then the gel mass finelydivided. In any case, the initially formed waxy particles may be furthersubdivided, or solvated, or both, to secure increased gelcosity, andthis is generally desirable.

In ordinary practice, I use the plan of solvating or gelling the waxwith the vehicle of the final product,,the wax being either introducedinto the whole amount of the vehicle at once, or being first combinedwith a portion of the vehicle and the remainder then added at anappropriate stage. Alternatively, the wax may be gelled with one liquidsubstance and the gel particles thereafter distributed in another liquidsubstance. In any case, a concentrated suspension product may beprepared containing more wax than is needed for stably suspending thepigment or other solid particles, and this concentrate may later bediluted by mixingwith the same or a different liquid.

The sulfur or other solid material, in powdered form, may be introducedat any stage of preparation, that is, it may be mixed with the vehiclebefore or after the wax is added; and if mixed in after the addition ofthe waxit may be added either before or after the wax has been reducedto a subdivided gelled state.

It is generally most convenient to incorporatethe .wax in the vehicle bydissolving th purpose, and then cooling the solution, preferably,

but not necessarily,'without a'gitation,.to a temperature at which mostof the wax insoluble at room temperature comes out of solution. The

of this material (particularly if it is not already. in a highlysolvated condition) to form-finely, di-' vided elastic gel particlesdistributed throughout the vehicle. This is accomplished by subjectingthe material to thoroug mechanical agitation. The mixture may be agiated by the action of a propeller type stirrer which is 'sufilcientlyvigorous, by being pumped and repumped through a mixing time pump, or bybeing milled in a ball divide the gel into fine particles.

or pebblemill, in a roll mill, or in a colloidal mill.

Pumping treatment may be conveniently performed with a gear pump, forexample, having an inlet pipe communicating with the bottom of a tank orother receptacle in which the mixture 5 valve disk from its seat to forma ring shaped orifice. The advantage of this type of orifice over anordinary fixed jet-orifice is that greater uniformity is obtained andclogging is avoided. When material is' deposited on the valve seat anddisk, the disk will automatically move away from the seat so as tomaintain the orifice and permit the deposited material to be washedaway.

It is generally preferable to mix the sulfur orother material to besuspended, in powdered form, with the wax-vehicle mixture before thelatter is subjected to mechanical treatment, or during the course ofsuch treatment, in order to distribute the sulfur or other particlesuniformly throughout the mixture at the same time that the finelydivided gel particles are being formed and distributed. The mechanicaltreatment in the presence of the waxmaterial assists in breaking up anddeagglomerating the solid material, and at the same time the sulfur orother particles increase the mechanical action on the wax par-' ticlesand facilitate their subdivision and solution. Grinding of sulfurmaterial in the vehicle of the productis often resorted to, and suchgrind-- ing may be performed following incorporation of wax inaccordance with the present invention, the grinding simultaneouslysubjecting the wax to the desired mechanical action.

Mechanical workingpf a severe nature is generally required to causeadequate solvation of wax in vehicles of the non-viscous organic solventtype, such as petroleum ether, naphtha, benzene, toluene, turpentine,alcohol, acetone, Cellosolve, carbon tetrachloride, and the like. Withrespect to incorporation of wax in these vehicles, it is not enough tomerely subdivide the wax material, and mechanical work is needed tocause the liquid to solvate the solid wax phase so as to obtain elasticgel particles. When viscous oil vehicles are used, the wax will usuallygel satisfactorily with the vehicle without agitation, that is, a gelwill be formed merely by cooling the initial hot 'solution of wax inoil, and a mere stirring will 55 produce a mixture which possessesgelcosity; al-' though agitation should be used in order to sub- When anonviscous vehicle is employed, cooling of the initial solution willgenerally result in a fiooculent wax g0 precipitate and the mixture willnot exhibit substantial gelcosity upon mere stirring, severemechanical'working being needed to cause liquid to dissolve in or beadsorbed by the wax particles.

A small amount of awetting agent may be 05 added to facilitatesubdivision of the wax or gel particles during mechanical working.Subdivision of the particles produces an increase in the, total surfacearea of the particles, resulting in an increase in the interfacial orsurface energy 70 of the particle system. The greater the magnitude ofthis energy the greater the resistance to further subdivision, and thegreater the tendency .of the particles to agglomerate in order todecrease the surface area and surface eneru. 2i

Under any given working conditions, for example with a particularpumping set up, the available kinetic energy acting on the individualparticles cosity) less definite value only, and no'smaller, the energyrequired for further subdivision being greater than that available. Byusing a wetting agent, which is adsorbed by the particles, the surfaceenergy per unit of surface area is made lower than it would beotherwise, and hence a greater subdivision and smaller particle sizewill be produced. Sulphonated castor oil (Turkey red oil) is an exampleof a suitable wetting agent and is effective when added to the waxvehicle mixture in amounts of a fraction of one percent. The wettingagent will also act as an agglomeration inhibitor for the wax particles,and may serve the same functions with respect tothe pigment or othersuspended particles. Other examples of suitable wetting agents are thosesold under the trade-names of Erkalin and Avirol.

The smaller the size of the gel particles, the

greater the suspending power (gelcosity) of the medium, and hence thesmaller the amount of wax needed.

Unless sufficient gel material is present to exist in equilibrium withthe liquid phase,'a serum layer will form even without the presence ofsulfur or other suspended solid particles in the gelatinous mass.sufilcient concentration of gel particles, due to insufficient waxhaving been incorporated, resulting in a settling of the gel particlesuntil in substantial contact, the mass of gel particles being surmountedby a serum layer of the liquid. If the wax particles are of lowerspecific gravity than the vehicle, the serum layer will form on thebottom of the container.

Even when substantially in contact, the iridi-' vidual gel particleswill tend to contract, with a resultant bleeding out of liquid containedtherein, until an equilibrium is established, if they have originallytaken up too much liquid; this effect being known as 'syneresis. Thismay be avoided by employing a greater amount of wax.

The presence of entrained sulfur or other par ticles of greater densitywill result in compression of a mass of gel particles, with the resultthat a portion of the liquid present in and betweenthe gel particles maybe squeezed out and'rise to the surface as a serum layer. This may beavoided by employing a sufficient amount of wax,

but the formation of a serum layer is not necessarily detrimental. Thatis, the formation of a serum layer does not mean, that the sulfur orother particles are not stably entrained and suspended in the mass ofgel particles, but it indicates that an excess of liquid is present.There is no settling of the sulfur or other particles to a cake orcompact layer on the bottom of the receptacle, as the sulfur or otherparticles will be stably suspended in the mass of gel particles(assuming that this mass possesses adequate gel- Gentle agitation orstirring will cause the serum layer to redistribute itself throughoutthe gelatinous mass to reform a completely uniform mixture.

The tendency to form a serum layer will be, counteracted by finelydivided air bubbles which become entrained during extended pumping orother mechanical agitation of the suspension during preparation.Sucndispersed air'globules" of small size will be held within thegelatinous mass and. will be mechanically prevented from This may becaused by an i'nparticles are prevented from settling, the force ofbuoyancy on the air particles being insufiicient to produce movement,owing to the gelcosity effect. The buoyant force of the air bubblestends to offset the downward drag of the suspended solid particles andreduces the compression exerted by the latter, thus reducing thetendency to form a serum layer. This effect may be further increased, tominimize any serum layer, by so conducting the agitation of the mixtureas to favor the entrainment of air. For example, a pumping arrangement,as hereinbefore described, in which the mixture is discharged from thecirculatingpump in a stream onto the surface of the main body, willcause splashing favoring the entrainment of air, and the pumping willtend to finely divide the bubbles thus incorporated. Air may also beforced into the pipe line and thus introduced, and this will beparticularly effective when the mixture is forced through a fine,orifice. This use of air for the minimization of serum layers isdescribed in more detail in the patent to V. R. Abrams, No. 2,007,137,issued July 2, 1935, to which reference may be made.

The following examples illustrate the preparation of sulfur suspensionshaving great value as cutting lubricants'and forother lubricationpurposes under extreme pressure and/or high .temperature conditions.Reference may be made to the patent to V. R. Abrams, No. 1,913,300,issued June 6, 1933, for details as to the lubricating.

action of sulfur suspensions.

Example! mainder of the oil (about 13%%) andthoroughlys agitate, .as bypumping through a small orifice, to produce smoothness of texture and afinely divided condition of the gel and sulfur particles.

Example 2 Melt and dissolve 3% of hydrogenated castor oil wax in 12%of'petroleum oil, such as a neutral. oil of 28-32{ Baum gravity, bystirring and and add 50% of petroleum' oil at about room temperature,producing cooling and gelling. Agitate by'pumping under pressure througha small orifice, or, in any suitable manner, to produce smoothness oftexture and finely divided gel particles. Add 1% of sulfonated castoroil and 15% of flowers of sulfur. Agitate" and stir to produce a uniformmixture containing finely divided sulfur distributed therethrough andstably suspended. Th 11 add 19% of oil and agitate an'd stir forabo tone hour.v

' This mixture provides a lubricant base of con-. centrated form whichthe user can dilute with two par? of petroleum oil to secure a freelyflowing ,utting lubricant containing stably suspended/sulfur particlesof greater than colloidal size.

Ayaluable feature resulting from the use of hydrogenated castor oil waxis that suflicient gelcosity and suspending power will be present evenif the user over-dilutes to the extent of producing 15:1 dilution, whichin this extreme case would mean that only of wax would be present.

Example 3 Melt and dissolve 1% of hydrogenated castor oil wax in about93 of petroleum oil, by stirring and heating to ZOO-250 F. Cool by anymeans to about F. Add about /3% of sulfonated castor oil (as commercialTurkey red oil) and about 5% of powdered sulfur. Then agitate and pumpunder pressure through a small orifice to produce smoothness of textureand a uniform distribution of finely divided gel and sulfur particles.

A freely flowing mixture is obtained in which the sulfur is held instable suspension, and it is adapted to be used directly as a cuttinglubricant.

This application is in part -a continuation of my copending applicationSer. No. 751,413, filed November 3, 1934, and is a division of myapplication Ser. No. 84,589, filed June 10, 1936.

In the claims the word solvated is used in its usual sense, meaningcompounded with a liquid to form a gel-like substance, similar tohydrated particles where water is the liquid.

I claim the following as my invention:

1. A freely flowing lubricant especially adapted for use underextreme-pressure and/or high temperature conditions, comprising amineral oil vehicle gelled with a small amount of hydrogenated castoroil wax, constituting a discontinuous gelatinous mass containing finelydivided gel particles and possessing the property of gelcosity, andfinely divided sulfur particles of greater than colloidal sizedistributed therethrough in an amount to function as a lubricatingingredient and be stably suspended therein.

2. A freely flowing lubricant comprising a mobile discontinuousgelatinous mass containing finely divided particles of elastic gelcomposed of mineral oil. and a small amount of hydrogenated castor oilwax, said particles being substantially in contact with each other andhaving the interspaces containing oil, and finely divided sulfurparticles of greater than colloidal size distributed therethrough andstably suspended therein to function as a lubricating ingredient.

3. A lubricant comprised of a mineral oil vehicle gelled withhydrogenated castor oil wax constituting a discontinuous gelatinous masscontaining finely divided gel particles and containing finely dividedsulfur particles of greater than colloidal size distributed therethroughin amount suflicient to function as an efiective lubricating ingredientupon a predetermined dilution, sufficient wax being employed to permitof a stable suspension of the sulfur upon said dilution when the gelledmaterial is in finely divided form.

4. A lubricant comprised of petroleum oil gelled with about 1 ofhydrogenated castor oil wax, constituting a discontinuous gelatinousmass containing finely divided gel particles and possessing the propertyof gelcosity, and about 5% of sulfur in the form of finely dividedparticles of greater than colloidal size distributed therethrough andstably suspended therein.

5. A freely flowing lubricant comprised of a mineral oil vehiclecontaining finely divided solid lubricant particles of greater thancolloidal size and finely divided gel particles distributedtherethrough, said gel particles being composed of mineral oil gelledwith hydrogenated castor oil wax and stably suspending said lubricantparticles, and said lubricant particles being substantially insoluble inthe mixture.

6. A freely flowing lubricant composed of a mineral oil vehicle gelledwith a small amount of hydrogenated castor oil wax, constituting adiscontinuous gelatinous mass containing finely divided gel particlesand possessing the property of gelcosity, and finely divided solidlubricant particles of greater than colloidal size distributedtherethrough in an amount to function as a lubricating ingredient and bestably suspended therein, said lubricant particles being substantiallyinsoluble in the mixture.

7. A freely flowing lubricant comprising a mini eral oil vehicle gelledwith a small amount of hydrogenated castor oil wax, constituting adiscontinuous gelatinous mass containing finely divided gel particlesand possessing the property of gelcosity, finely divided sulfurparticles of greater than colloidal size distributed therethrough in anamount to function as a lubricant ingredient and be stably suspendedtherein, and a wetting agent to inhibit agglomeration of said sulfurparticles.

8. A lubricant comprising a mobile discontinuous gelatinous masscontaining finely divided particles of elastic gel composed of mineraloil and a small amount of hydrogenated castor oil wax, said particlesbeing substantially in contact with each other and having theinterspaces containing oil, finely divided sulfur of greater thancolloidal size distributed therethrough in amount to function as a.lubricating ingredient and be stably suspended,

and a small amount of sulfonated castor oil as an agglomerationinhibitor. 7

9. A freely flowing lubricant comprised of petroleum oil gelled withabout 1% of hydrogenated castor oil wax, constituting-a discontinuousgelatinous mass containing finely divided gel particles and possessingthe property of gelcosity, about 5% of finely divided sulfur of greaterthan colloidal size suspended therein, and about 6% of sulfonated castoroil.

10. A lubricant comprising a mineral oil vehicle gelled with a smallamount of hydrogenated castor oil wax, constituting a discontinuousgelatinous mass containing finely divided gel particles, finely dividedsolid lubricant particles of greater than colloidal size distributedtherethrough, and a small amount of sulfonated castor oil.

11. A lubricant base'comprised of petroleum oil gelled with about 3% ofhydrogenated castor oil wax, constituting a discontinuous gelatinousmass containing finely divided gel particles, about 15% of finelydivided sulfur particles of greater than colloidal size distributedtherethrough, and about 1 of sulfonated castor oil.

12-. A freely flowing suspension comprising a freely flowing viscousvehicle in which hydrogenated castor oil wax is lyophilic and relativelyinsoluble at room temperature, containing finely divided particles ofhydrogenated castor oil wax gelled with the vehicle and finely dividedsulfur particles'distributed therethrough in a suspended state, the waxbeing in amount to stably suspend said sulfur particles withoutpreventing free flow,

vrc'roa R. ABRAMS.

